Cyanoethylated cellulose textiles modified with chromic and periodic acids and process of making same



United States Patent Harry Weisberg, New York, N. Y., assignor to Londat Aetz Fabric Co., Elizabeth, N. New Jersey No Drawing. Application August 9, 1954, Serial No. 448,781

14 Claims. (Cl. 8--116.2)

This invention relates to methods of chemically modifying cellulose and the resultant products.

Cellulose in various forms has been treated with caustic soda and acrylonitrile for the purpose of decreasing moisture absorbency, increasing tensile strength and abrasion resistance and improving the surface lustre. It has been found that such cyanoethylated celluloses are'somewhat soluble in alkaline solutions but that the insoluble residue formed a gummy conglomerate. Furthermore, the relative solubility of such products in alkaline solution is of a relatively low order. a

A chemically modified cellulose in fabric form, which is readily soluble in alkali, is especially adapted for use as a backing material in lace manufacture. The laces are stitched on the backing fabric and such combination is placed in an. alkaline dissolving bath. which dissolves the backing fabric, leaving the lace structure intact.

To be suitable for use as a lace backing fabric, such fabric must have a high order of solubility and be adapted to free itself quickly and readily from the lace structure in the dissolving bath. Cyanoethylated celluloses known in the art have been found unsuitable for such use be cause of their relatively low degree of solubility in alkali. Furthermore, the dissolving action produces a gummy conglomerate on the surface of the material, thereby re stricting further solution of the material, which in turn prevents free separation of the backing from the lace.

Chemically modified cellulose, as well as silk and wool, have been used as backing fabrics for lace structures. However, such backing fabrics require a relatively high concentration alkali dissolving bath, 2% sodium hydroxide or even higher concentrations being used for such purpose. With baths of such high alkalinity, it has been impossible to use silk, wool, dyed fibers, tinsel or other alkali sensitive materials to form the lace structure which is stitched to the backing fabric.

An object of this invention is to further modifycellulose that has been treated with alkali andacrylonitrile, in order to increase the solubility of the end product in alkaline dissolving baths having a wide range of concentrations.

Another object of thisinvention is to form a modified cellulose of the type described wherein the acrylonitrile treatment is of relatively short duration and the cyanoethylated cellulose is further treated with chromic or periodic acids to produce an end product which is highly soluble in alkali of a relatively narrow concentration range.

Still a further object of this invention is to produce modified celluloses having a high degree of solubility in alkali wherein the insoluble, residual portions are of a non-gummy nature.

Still another object of this invention is to provide a cellulose fabric, treated as such with alkali, acrylonitrile and other reagents, or derived from fibers and the like so treated, the treated fabric being highly soluble in very dilute alkali solutions, such solutions having an alkalinity so reduced as to be substantially harmless to alkali sensi- J., a corporation of 2,724,632 Patented Nov. 22, 1955 tive materials such as silk, the like. Such a treated fabric may be used as a backing for stitching thereon lace formed of silk, wool, dyed fibers or tinsel, the lace being separated in a mild alkaline bath which readily dissolves the backing yet leaving the lace unharmed.

When cellulose is subjected to the alkali-acrylonitrile treatment, followed by further treatment with chromic or periodic acids, the flammability of the end product is increased as compared to that of the original, untreated cellulose. A further object of this invention is to reduce the flammability of the modified cellulose of the instant invention by further treating the same with chemical reagents which form a reaction product in situ and integrated therein, the reaction product being irremovable from the modified cellulose by washing.

Yet a further object of this invention is to provide a chemically modified alkali-acrylonitrile impregnated cellulose having the improved properties mentioned above, the modification being such as to result in a relatively small amount of degradation and to retain substantially the original strength of the untreated cellulose.

Yet another object of this invention isto provide a chemically modified cellulose and more specifically, a uniformly cyanoethylated cellulose free of harshness and having a soft hand.

. Still another object of this invention is to provide chemically modified cellulose of the character described which displays excellent resistance to mildew and greater receptivity for dyes applied thereto.

Still a further object of this invention is to provide improved dissolving baths for increasing the solubility of alkali solutions of commercial, intermediate concentra-.

tions, and very slight solubility in solutions of very weak or very strong concentration.

However, it was found that if the alkali-acrylonitrile treated cellulose was further subjected to the action of chromatic or periodic acid, the resultant product was further chemically modified and was highly soluble in alkali solutions of very weak concentrations, as well as in solutions of substantial strength. Furthermore, the insoluble residue was quite small in amount and was not of a gummy or sticky nature.

Unlike other cellulose ethers, including the known cyanoethyl ethers, the product of this invention dissolves in alkaline baths substantially without the usual swelling effect. As is well known in the art, known cyanoethyl ethers start to dissolve with an initial swelling of the surface layers. Such swelling action prevents the solution of the inner fibrils of the mass and thus causes a gummy conglomerate to form. Obviously, this type of partial solution presents a serious problem when high solubility and rapid solution is required.

It is apparent that known cyanoethyl ethers have solubility characteristics which render them unsuitable for use with the instant invention may be in fibrous or non-fibrous form, woven or felted and may be constituted of cotton, linen, ramie, jute, regenerated cellulose, woodfiber or pulp, or selected admixtures thereof.

wool, dyed fibers, tinsel and Essentially, the novel process comprises the treatment of cellulose'with a strong hydroxide and acrylonitrile, followed by further treatment with chromatic or periodic acid. The cellulose suffers relatively little degradation and retains substantially the original tensile strength.

The strong hydroxide used may include sodium, potassium or lithium hydroxide, or a quaternary ammonium hydroxide such as benzyl trimethyl quaternary ammonium hydroxide, dibenzyl dimethyl ammonium hydroxide, and the like. The concentration of the hydroxide may vary from about 3% to about 50% and the treating temperature from about 20 C. to boiling, it being understood that temperature and concentration are suitably correlated. r

The impregnation of the cellulose with the hydroxide may take place in a relatively short interval of time, since the reaction is very rapid. Sufficient impregnation may be achieved in about a minute, however where the cellulose is in the form of a heavier fabric or with higherconcentrations of the sodium hydroxide, longer treating intervals may be used and which may be extended to a day or more, if desired. Preferably, the hydroxide may be used in concentrations ranging from about 10% to about 30% and the treating temperature varying between about C. to about 50 C.

The acrylonitrile is used in concentrations varying from about 1% solution to full strength commercial grade. When diluted, the acrylonitrile may be dissolved in an inert, water immiscible solvent such as benzene, toluene, xylene, carbon tetrachloride, petroleum distillate, solvent naphtha, cyclohexane or mixtures thereof. The acrylonitrile may also be dissolved in an aqueous solution of strong hydroxide, thus combining the hydroxide impregnation and acrylonitrile reaction in a single step. However, the use of acrylonitrile. in the inert, water immiscible type of solvent is preferred.

The acrylonitrile treating interval may be very short, satisfactory results having been obtained with as little as a half minute treatment, but such treating period may be extended to as much as 24 hours or more when a greater degree of cyanoethylation is desired. The treating temperature may be varied from as low as 0 C. up to the boiling temperature of theimpregnant.

Two general types of modified cellulose which are highly soluble in alkaline solutions, may be produced in accordance withthe instant invention.

One type of modified cellulose has a high degree of solubility in alkaline solutions having a wide range of concentrations, thus being soluble in 30% sodium hydroxide as well as in hydroxide having a concentration as low as 0.02%. This form of modified cellulose requires treatment with the acrylonitrile for about a half hour or longer.

The other type of modified cellulose has a highdegree of solubility in alkali concentrations of a relatively nar-. row range, as from about l0% to about. 20% sodium hydroxide. This form of modified cellulose requires a short treatment with acrylonitrile which may range from about a half minute to about one half hour.

The hydroxide impregnation used to form either type of modified cellulose, is substantially unchanged and is carried out as: previously described. The treatment of the hydroxide-acrylonitrile modified cellulose, with chromic. or. periodic. aei d, as, will, be. described in detail, is also substantially unchanged for. the two types of alkali soluble'rnodified cellulose described above.

It willbe apparent that the conditions under which the acrylonitrile impregnation is carried out will determine the type of modified cellulose produced, in terms of: the; solubility characteristics thereof in alkaline solutions.

Informing the first mentioned type of modified cellulos'e' whicli is" soluble in alkaline solutions over a wide range of concentrations; the acryionitrile impregnation interval should be at least about one half hour or longer and the temperature and concentration ranges of the impregnant being of the order previously described.

In making the second mentioned type of modified cellulose and using the short interval of acrylonitrile impregnation, i. e., from about one half minute to about a half hour, the temperature of the impregnant should not fall below about 15 C. and should preferably be about 20 to about 30 C., but may be increased to the boiling point thereof. The concentration of the acrylonitrile impregnant may be varied from about 1% to full commercial strength, but is preferably about 5% or greater.

it is understood that the cellulose in selected form may be first treated with the strong hydroxide and followed by treatment with acrylonitrile, or the order of impregnation may be reversed. However, the first mentioned sequence of steps is preferred. In either case, the excess hydroxide and acrylonitrile is removed from the cellulose by squeeze rolls or other suitable means. The treated cellulose is washed and residual hydroxide is neutralized by application of any suitable acid such as hydrochloric, sulfuric, oxalic or acetic acids, or any other suitable neutralizing agents. The treated cellulose is then again washed.

The cyanoethyl ether of cellulose thusformed is then further modified by immersing the same in a bath of chrornic or periodic acid. The concentration of the acid bath may vary from about 0.5% upwardly to about 50%. The time interval for impregnation decreases as the acid concentrationincreases. A preferred range of acid concentration is from about 2% to about 15%. With higher acid concentrations, very short impregnation intervals are sufilcient, e. g., the impregnation time for a 50% solution of chromic acid is of the order of several seconds.

The acid impregnation interval is similarly related to the treating. temperature as it is to the concentration. Thus with a 5% chromic acid solution, the impregnation period is about one half hour at room temperature and about a half minute at boiling temperature. An acid solution with a concentration of about 2% to 3% requires I an impregnation period of about 24 hours at room temperature. It is noted that solutions of dichromate or periodate salts and an acid such as sulfuric, hydrochloric or nitric acid, may be used in lieu of the chromic and periodic acids. Furthermore, the acids may be mixed to provide the impregnating bath.

It will be apparent that in the acid treatment step, various combinations of concentration, temperature and time intervals may be used, within the limitsdescribed above. For a rapid reaction, one may use a 5% solution of acid at a boil for. about one half minute while a similar solution used at room temperature, the impregnation interval may be extended to about one hour. In all cases, the desired reaction is. carried to a point where the modified cellulose is highly soluble in alkaline solutions as described above and to such point that there is substantially no degradation or accompanying tenderization of: the treated material. When the cellulose is originally in the form of fabric, fiber or linters', the original physical form is retained after treatment and the endproduct retains a substantial portion of its original tensile strength. The thus treated material may then be washed and dried.

Asaresult of the sequential treatmentof the cellulose, as described, the end product shows somewhat increased flammability. If it; is desired to reduce the flammability thereof the modified cellulose is further treated with. a solution of a salt of a weak ionized acidand a metal cation in the presence of a weakly ionized acid. The excess treating salt and acid. is removed; from the treated material by thorough washing. The resulting product not only retains its strength, physical appearance and excellent solubility in alkaline solutions, but in addition, has its flammability substantially reduced. Since further washing .of the treated material leaves the improved flammability characteristics: thereof: unchanged, it is probable that a reaction: in situ has taken place as between the modified celluloseand the after appliedsalt-acid reagents.

Suitable salts include sodium formate, sodium oxalate, potassium citrate, sodium tetraborate, lead acetate, uranium acetate and the like. Suitable weakly dissociated acids include formic, acetic, oxalic, boric and citric acids, and the like. The concentration of the salt-acid bath may be suitably varied in terms of the treating temperature and impregnation interval. With higher concentrations, shorter treating intervals and lower temperatures may be used. Thus, with a solution of sodium formate in water in the presence of a 1% solution of oxalic acid, at a boil, the modified cellulose may be suiiiciently treated within a few minutes, removed from the bath, washed and dried.

It has been found that:the reaction described above is rather rapid and that extended treatment periods or higher salt and acid concentrations are unnecessary. With salt concentrations as low as 1% and acid concentrations as low as 0.5%, an impregnation interval of about one minute will give satisfactory results. With impregnation taking place at room temperature or lower, more extended treating intervals of about an hour or more is required.

The following example will illustrate the formation of the first mentioned type of modified cellulose which shows high solubility in alkaline solutions having a wide range of concentrations.

Example 1 Cotton fabric of the cheesecloth type wasimpregnated withan aqueous solution of 15% sodium hydroxide for about 3 hours at room temperature. Excess hydroxide was removed from the fabric with squeezing rolls. The treated fabric was then immersed in a bath of acrylonitrile of about by volume in carbon tetrachloride and retained therein from about 18 to about 24 hours. The treated material was then removed, washed with water and residual hydroxide in the material was soured with dilute sulfuric acid. Neutralizing acid was removed by washing. 1 t

The thus treated fabric was submerged in a bath of 5% chromic acid for about an hour at roomternperature, removedfrom the bath, washedin hot water, then in cold water and dried. The resultant product showed goodtensile strength and retained its original physical appearance.

The modified cellulose fabric thus produced was tested for solubility inalkaline solutions. Similar size samples of the material were each boiled for 10 minutes in 100 cc. of caustic soda solution, the level thereof being kept constant. The resultant solution was cooled, filtered in a gooch, the residue being washed and weighed.

Solubilities were determined for fabric samples subjected only to the hydroxide-acrylonitrile treatment and for samples so treated and additionally treated with chromic acid. The concentration of the caustic soda dissolving bath was varied as indicated below:

Percent solu- Percent solugg gz ble matter ble matter S (12;. in in hydroxidein hydroxidedi 01V, acrylon itrileacrylonitrilebath g treated acid treated fabric fabric cyanoethylation; With degrees of substitution in the lower range ofnitrogen contents, i. e., those corresponding to a nitrogen content of about 0.5%, required somewhat higher concentrations of the caustic soda dissolving bath to attain the highest degree of solubility.

Cellulose fabric treated with hydroxide-acrylonitrileacid, as described, is particularly adapted for use as a lace backing fabric which has the lace structure stitched thereon, followed by immersion in a dissolving bath to separate the lace structure from the dissolved backing. However, with the novel backing fabric made in accordance with the instant invention, high solubility is attained even in baths having a very low degree of alkalinity. Thus it has been found that when such treated cellulose has a degree of substitution of about one cyanoethyl group per anhydroglucose unit, the material is highly soluble in solutions such as 0.02% sodium hydroxide as well as in Weak alkaline solutions of sodium carbonate, sodium oxalate, trisodium phosphate, soap and the like.

Accordingly, alkali sensitive materials such as silk, wool, tinsel and the like may be stitched to the novel backing fabric, the combination being immersed in a bath of very low concentration hydroxide, alkaline salts or mixtures thereof to readily dissolve the backing and leaving lace structure undissolved or otherwise adversely affected. It is to be noted that in conventional lace making operations, backing fabrics are formed of silk or wool or other chemically processed materials which will readily dissolve in the usual dissolving bath which has a concentration of the order of 4% sodium hydroxide. Other alkali sensitive materials such as dyed fibers and metallic filaments may be used in forming the lace structure on the novel backing fabric, as described above. It is understood that a lace structure made up of cotton, may also be processed on the novel backing fabric.

Further examples follow, illustrating the formation of the second type of modified cellulose mentioned above.

Example II Percent Acrylonitrile treating time soluble matter 0.5 minutes 84. 0 3.0 minutes 86. 5 5.0 minutes 92. 8 15.0 minutes 94. 0

A further sample of fabric treated as described above with the 15.0 minute impregnation with acrylonitrile, was dissolved in a 6.0% sodium hydroxide solution, giving a solubility of 66.2%, thus indicating the effect of a weaker dissolving bath.

Example III Cotton fabric was impregnated with an aqueous solution of 20% sodium hydroxide for about 15 minutes at 35 C., excess hydroxide being removed by squeezing. One sample cut from the treated fabric was treated with acrylonitrile at 28 C. for 5 minutes and thereafter treated with chromic acid as in Example I. The thus treated sample had anitrogen content of 0.55% and a solubility of 93.0% in boiling 12.5 sodium hydroxide.

Another sample cut from the hydroxide treated fabric was treated with acrylonitrile solution for 15 minutes at a temperature of 15 C. The treated sample was washed and further treated with chromic acid as in the case of the first sample. The nitrogen content of the end prodnot was .55 and the solubility ina boiling 12.5 solu tion of sodium hydroxide was 82%. It was noted that the dissolution of the first sample took placemore rapidly than in the case of the Second sample and the residue of the former consisted of fine particles whereas the residue of the latter was stringy in nature.

Further samples cut from the original hydroxide treated fabric which were treated for short time intervals with acrylonitrile at temperatures well below 15 C., followed by the chromic acid treatment, showed even lower solubilities in alkaline solutions.

It was found that the dissolving powers of caustic soda baths were substantially enhanced upon the addition thereto of hydrogen peroxide. Additions of up to by volume of 25 volume hydrogen peroxide to the dis= solving bath gaveexcellent results in dissolving cyanoethyl cellulose. The peroxide can also be added to baths made up of potassium or lithium hydroxide or of a quaternary ammonium hydroxide.

Example IV Cotton fabric treated with sodium hydroxide and acrylonitrile, as generally described above and having a nitrogen content of about 5.0% was dissolved in a bath of 4% aqueous sodiumhydroxide having varying amounts of hydrogen peroxide added thereto, with the corresponding solubilities, as indicated below.

I Eercent soluble cc; of 25 volume HaOi in each 100 cc. NaOH nitril'e to form a cyanoethylated cellulose ether, the resultant product was harsh to the touch and appeared to be non-uniformly treated as evidenced by the non-uniform appearance thereof and irregularity in the feel of the material.

The same non-uniformity of appearance and harshness of hand was noted when the eyanoethylated cellulose was further. treated with chromic acid or periodic acid in accordance with the instant invention.

However, when small amounts of alkylnitriles such as succinonitrile, beta chloropropionitrile o'r adiporiitrile were added to the acrylonitrile bath, the cyanoethylated cellulose products obtained had a surprisingly soft hand and were of uniform appearance. Furthermore, whensuch products were subjected to further modification as by chromic or periodic acid, or when dyed or bleached,- thei desirableuniformit-y of appearance and soft hand was maintained.

7 The alkylnitrile may be used in relatively low concentrations, with from about 0.1% to about 1.0% thereof in the acrylonitrile producing the desired effects. Thealkylnitrilemay be directly addedto the acryloni-trilein-pure rwhen solution. Ifnecessary a; mutual solvent unmanned the acrylonitrile may be used. Thus, acrylon'it'ril'e in carbon tetrachloride, suceino- This was particularly apparent when the cyanoethylated cellulose was in the form of fabric or yarn.

nitrile may be first dissolved in chloroform which is then added to the acrylonitrile solution.

Example V Cotton cheesecloth was passed through a sodium hydroxide solution for an impregnation interval of about 1 minute at C. The impregnated fabric was squeezed to remove excess hydroxide and was then soaked in a bath of acryl o'nitrile in carbon tetrachloride at 25 C. for about 1 minute. The thus treated fabric was washed and excess alkali was neutralized by souriiig in a 5% sulfuric acid solution. Excess acid was removed by washing.

The treated fabric was subjected to a 5% solution of periodic acid at a boil for about 1 minute. The final product tested for solubility in 12.5% sodium hydroxide, as previously described, showed 98.0% solubility.

It has been found that cellulosic materials in fabric or other forms, which have been treated in accordance with the instant invention, show substantial resistance to mildew, and furthermore, is adapted to take dyes more receptively.

This application is a continuation in part of copending applications Serial No. 288,043, filed May 15, 1952, and Serial No. 347,843, filed April 9, 1953, said applications being now abandoned.

As it is apparent that many different embodiments may be made within the spirit and scope of the invention, it is to be understood that the invention is not limited to the disclosed embodiments except as set forth in the claims following.

Having thus described my invention, I claim as new and desire to protect by Letters Patent:

1. The process of forming chemically modified cellulose comprising impregnating textile cellulose with a strong alkaline hydroxide solution of a concentration of from about 3% to about at a temperature of from about 20 C. to boiling for at least about a minute, removing excess hydroxide from the impregnated cellulose, reacting the impregnated cellulose with acrylonitrile to form cyanoethylated cellulose containing nitrogen by weight of from about 0.5% to about 12.5% of the cyanoethylated cellulose; and thereafter impregnating the cyanoethylated cellulose with a solution of an acid selected from the group consisting of chromic and periodic acids having a concentration of from about 0.5 to about 50% at a temperature of from room temperature to boiling for a period of from about a few seconds to about 24 hours, the time and temperature of said acid impregnation being inversely related to the acid concentration to form chemically modified cellulose which retains a substantial portion of the original strength of the untreated cellulose and which is highlysoluble in alkaline dissolving baths.

2. The process of forming chemically modified cellulose which is highly soluble in alkaline solutions of a con centration of from about 0.02% to about 30%, comprising impregnating textile cellulose with sodium hydroxide solution having a cencent-ration of from about 10% to about 30% at a temperature of from about 0 C. to about 50 C. for aperiod of from about a minute to about 24 hours; removing excess hydroxide from the im pregnated cellulose, reacting the impregnated cellulose with acrylonitrile to form cyanoethylated cellulose having a nitrogen" content by weight of from about 0.5% to about 12.5% of the cyanoethylate'd cellulose; and thereafter impregnating the cyanoethylated cellulose with chromic acid solution of a concentration of from about 2% to about 15% at a temperature of from room temperature to boiling for a period of from about a few seconds to about 24 hours, the time and temperature of the acid impregnation being inversely related to the acid concentration to form chemicallymodified cellulose having a substantial portion of the original strength of the untreated cellulose. h

3. The process of forming chemically modified cellulose which is highly soluble in alkaline solutions of a concentration of from about 10% to about 20%, comprising impregnating textile cellulose with sodium hydroxide solution of a concentration of from about 3% to about 50% at a temperature of from about -20" C. to boiling for from about a minute to about 24 hours, removing excess hydroxide, from the impregnated cellulose, reacting the impregnated cellulose with acrylonitrile for a period of from about /2 minute to about /2 hour at a temperature of from about 20 C.to about 30 C. to form cyanoethylated cellulose having a nitrogen content by weight within the range pf from about 0.5% to about 12.5% of the cyanoethylated cellulose; and thereafter impregnating the cyanoethylated cellulose with a chromic acid solution of a concentration of from about 0.5% to about 50% at a temperature of from room temperature to boiling for a period of from about a few seconds to about 24 hours, the time and temperature of said acid impregnation being inversely related to the acid concentration to form chemically modified cellulose which retains a substantial portion of the original strength of the untreated cellulose.

4. The process of claim 1 wherein the reaction of the impregnated cellulose with acrylonitrile extends over a period of from about /2 hour to about 24 hours, the resultant chemically modified cellulose being highly soluble in alkaline solutions ofconcentrations of from about 0.02% to about 30%.

5. The process of forming chemically modified cellulose comprising impregnating textile cellulose with a strong alkali hydroxide of a concentration of about 15% for about 3 hours at room temperature, removing excess hydroxide from the impregnated cellulose, reacting the impregnated cellulose with a 10% solution of acrylonitrile for about 18 hours to form cyanoethylated cellulose, and impregnating the cyanoethylated cellulose with 5% chromic acid for about 1 hour at room temperature to form chemically modified cellulose having a substantial portion of the original strength of the untreated cellulose and which is highly soluble in alkaline solutions.

6. The process of forming chemically modified cellulose comprising impregnating textile cellulose with a strong alkali hydroxide of a concentration ofabout 15% for 3 minutes at room temperature, removing excess hydroxide fromthe impregnated cellulose, reacting the impregnated cellulose with acrylonitrile for about 5 minutes at a temperature of about 25 C. to form cyanoethylated cellulose, and impregnating the cyanoethylated cellulose with 5% chromic acid for about 1 hour at room temperature to form chemically modified cellulose having a substantial portion of the original strength of the untreated cellulose and which is highly soluble in alkaline solutions having a concentration of from about to about 20%.

7. The process of claim 1 wherein the textile cellulose is cyanoethylated in the presence of a small amount of an alkyl nitrile selected from the group consisting of succinonitrile, adiponitrile and beta chloroproprionitn'le to give the chemically modified textile cellulose a soft hand.

8. The process of claim 1 wherein the acid treated 10 cyanoethylated textile cellulose has its flammability reduced by being further impregnated with an acidified aqueous solution of a compound selected from the group consisting of sodium formate, sodium oxalate, potassium citrate, lead acetate and uranium acetate.

9. Chemically modified textile cellulose produced by the process of claim 1.

l0. Chemically modified textile cellulose produced by the process of claim 7.

ll. Chemically modified textile cellulose produced by the process of claim 8.

12. A lace backing fabric comprising a Woven cotton fabric modified by the process of claim 1, the modified backing fabric substantially retaining the form and strength of the untreated fabric.

13. The method of forming lace from textile materials degraded or corroded by alkaline solutions of high alkalinity of the order of a 4% solution of sodium hydroxide and substantially unaffected by alkaline solutions of low alkalinity of the order of a 0.02% solution of sodium hydroxide comprising forming a lace structure of said textile materials on a chemically modified cellulose backing fabric produced by the process of claim 1, immersing the combined lace structure and backing fabric in an alkaline solution of said low alkalinity until said backing fabric is dissolved and said lace structure is released, said lace structure being substantially unaflfected by said alkaline solution of low alkalinity.

14. The method of dissolving the chemically modified textile cellulose of claim 9 comprising immersing said modified cellulose in a dissolving bath of an aqueous 4% solution of sodium hydroxide containing from about 1% to about 10% by volume of 25 volume hydrogen peroxide.

References Cited in the file of this patent UNITED STATES PATENTS 1,261,736 Ferguson Apr. 2, 1918 1,823,847 Balle et a1. Sept. 15, 1931 2,015,104 Dreyfus Sept. 24, 1935 2,184,041 Harold Dec. 19, 1939 2,339,277 Luckhaupt Jan. 18, 1944 2,339,797 Bock et al May 30, 1944 2,390,032 Stallings Nov. 27, 1945 2,390,033 Stallings Nov. 27, 1945 2,422,572 Lilienfeld June 17, 1947 2,424,831 Klaber July 29, 1947 2,444,022 Buurman June 29, 1948 2,488,485 Winternitz Nov. 15, 1949 2,525,514 Barkey et al. Oct. 10, 1950 2,555,446 Hutchinson June 5, 1951 FOREIGN PATENTS 588,751 Great Britain Mar. 8, 1946 219,790 Germany Mar. 8, 1910 OTHER REFERENCES Somers: New Family of Rayons, British Rayon and Silk Journ., May 1950, pp. 62, 63 and 88. 

1. THE PROCESS OF FORMING CHEMICALLY MODIFIED CELLULOSE COMPRISING IMPREGNATING TEXTILE CELLULOSE WITH A STRONG ALKALINE HYDROXIDE SOLUTION OF A CONCENTRATION OF FROM ABOUT 3% TO ABOUT 50% AT A TEMPERTURE OF FROM ABOUT-20*C. TO BOILING FOR AT LEAST ABOUT A MINUTE, REMOVING EXCESS HYDROXIDE FROM THE IMPREGNATED CELLULOSE, REACTING THE IMPREGNATED CELLULOSE WITH ACRYLONITRILE TO FORM CYANOETHYLATED CELLULOSE CONTAINING NITROGEN BY WEIGHT OF FROM ABOUT 0.5% TO ABOUT 12.5% OF THE CYANO ETHYLATED CELLULOSE; AND THEREAFTER IMPREGNATION THE CYANOTHYLATED CELLULOSE WITH A SOLUTION OF AN ACID SELECTED FROM THE GROUP CONSISTING OF CHROMIC AND PERIODIC ACIDS HAVING A CONCENTRATION OF FROM ABOUT 0.5% TO ABOUT 50% AT A TEMPERATURE OF FROM ROOM TEMPERATURE TO BOILING FOR A PERIOD OF FROM ABOUT A FEW SECONDS TO ABOUT 24 HOURS, THE TIME AND TEMPERATURE OF SAID ACID IMPREGNATION BEING INVERSELY RELATED TO THE ACID CONCENTRATION TO FORM CHEMICALLYB MODIFIED CELLULOSE WHICH RETAINS A SUBSTANTIAL PORTION OF THE ORIGINAL STRENGTH OF THE UNTREATED CELLULOSE AND WHICH HIGHLY SOLUBLE IN ALKALINE DISSOLVING BATHS. 